To recognize or sense a weakness or vulnerability (especially a new one) in an opponent, adversary, or subject over which one is trying to gain an advantage. The phrase implies that such a weakness will then be acted upon to gain victory or advantage. The visiting squad is starting to look tired, and the home team scents blood. Look for them to try to close out the game. Do not give any indication that we are willing to settle. If we do, the attorneys will scent blood and we won't get what we want.